i posted a topic about two weeks ago about my 400 scrambler making a vibrating sound. i was really worried for a while because it almost sounded like it was coming from the engine. i thought maybe i didn't break it in properly. well i was determined to find the source of the vibration. well it didn't take long or take a rocket scientist to figure out what it was, i was relieved. i looked under the front and started banging on stuff while the quad was turned off. as soon as i hit the little plastic cover that covers the front drive shaft..... bingo. the darn thing must have had some kind of little clip to hold the front of it to that metal prong sticking up, well, whatever was there isn't anymore. glad it was something real stupid like that. took a old tire tube and cut a piece of rubber off pushed it onto the metal prong. it holds it well. nothing like alittle afro engineering. oops, i don't think i was supposed to say that on here. what really goes on there? i would like to put the proper fastener back on

 

I had a similar expieriance. When mine was new, I kept hearing a banging & knocking sound down low. Sounded like it was coming from the engine or transmission. It didn't stop, and the reliability horror stories came to mind. I pulled of the skidplate when washing it and a bunch of rocks & stocks came out. After that, no noise!